Catalytic alkylation of aromatic hydrocarbons by paraffins



Dec. 23, 1947. s, B, BECKER 2,433,020

CATALYTIG ALKYLATION or ARoMA'rIc HYDROCARBONS mt4 FARM-FINS I Patented-Dec.v A23; 1947 l UNITED STATE CATALYTIC ALKYLATION OF ARO HYDROCARBNS BY PARAFFIN S l A'rrc v Sam B.' Becker, Chicago, Ill., assignor to Standard Oil l Indiana Company, Chicago, Ill., al corporation o! Application August 14, 1944, serial no. 549,449 s claims. (ci. aso- 671) t with olefins by means of such catalysts as aluminum chloride, hydrogen iiuoride, aluminum chloride `promoted by hydrogen chloride, hydrogen, iluoride-boron fluoride mixtures, etc.; `an object of myinvention is to provide a process which does not require the use of oleflns or of l halogenated hydrocarbons but which can utilize paraiiin hydrocarbons per se, particularly isoparaflins. Aromatics have been alkylated with parains with such catalysts as sulfuric acid, phosphoric acid and aluminum chloride-hydrogen chloride catalysts; an object of my invention is'` to avoid the charging stock degradation and catalyst losses which characterize these prior processes. A further object of my invention is to provide an improved method and means for producing valuable high antiknock gasoline components which are particularly valuable for aviation gasolines. A further object is to pro- -vide an improved method and means for producing alkyl benzenes directly from parains and aromatics and to avoid the necessity of concentrating or even employing olenns in the process. A further object is to increase the simplicity and efficiency of such a process andto decrease the construction and operating expense thereof. A further object is to provide an improved method and means for minimizing catalyst losses even when hydrocarbon gases are vented from the system.` Other objects will be apparent as the detailed description of the invention proceeds.

In practicing my invention I contact an aromatic hydrocarbon such as benzene with an isoparaiiin such as isooctane with a catalyst comprising hydrogen uoride at a temperature inthe general lvicinity of 400 F. and under a pressure of about 1200 to 1300 pounds per square inch with intimate mixingfor a period of time of about hours to produce alkyl benzenes such as tertiary butyl benzene.

Instead of employing benzene as the aromatic hydrocarbon I may employ an alkyl benzene such as toluene, xylenes, etc. or a mixture of such alkyl benzenes or a mixture of benzene with one or more alkyl benzenes. Also, I may employ di- 2 cyclic aromatics such as naphthalene, diphenyl, etc., polycyclic aromatics such as anthracene, and alkyl dicyclic and polycyclic aromatics. Substituted aromatics may be employed provided that the substituting group is not affected by the catalyst under conversion conditions.`

The paraffin hydrocarbons are preferably isoparalns such as'isobutane, isopentanes, isoheptanes, isooctanes, etc. or mixtures of 2 or more thereof` with each other or with normal parains. I- have found that normal paraftlns per se require much more severe operating conditions than isoparailns, i. e. the use of considerably higher temperatures and pressure or the use oi?y promoters such as boron iiuoride. The charging stock is preferably substantially free from olens since the presence of olens tends toward .the formation of alkyl fluorides; however, small amounts of olens may be tolerated.

The reaction conditions will depend to a considerable extent upon the particular charging stock and the nature of the desired conversion. In all cases I prefer to employ a relatively large volume of catalyst and theratio of hydrogen fluoride'to hydrocarbon in the react'or may, for example, be within the approximate range of n 1:1 or highery although benecial results may be obtained with catalyst to hydrocarbon ratios within the approximate range of 10:1 to 1:10.V

'I'he mol ratio of aromatic to paraiiin may be within the approximate range of 1:2 to 100:1 or higher, good results having been obtained with a ratio of 2:1 and 1:1. The mol ratio will depend to a considerable extent on the nature of the desired product and an excess of parailins may be employed for the net production of isoparafns along with alkyl benzenes.

The temperatures employed will likewise vary throughout a, considerable range in accordance with thejparticular charging stocks employed and the nature of the desired products. Temperatures in the general vicinity of 400 F. are

, suitable for the alkylation of aromatics with isoparaflins but when normal parains are employed temperatures' as high as 600 to 700 F. may be necessary unless promoters are used. However, when about 5% boron fluoride is used as a promoter, a normal paraiiin such as heptane will effect a'lkylation of benzene at a temperature of about 330 F. to produce ethyl benzene as the main alkylation product along'with considerable amounts of isoparafllns and higher boiling alkyl benzenes. I may employ a hydrogen fluoride .catalyst containing between about 2 and 20 weight per cent of boron fluoride and may effect alkylation therewith at a temperature not substantially higher than about 400 F. Instead u catalyst in the form conventionally employed for eiiecting hydrogenation. A trace ofrwater may also act as a promoter but the amount of water should preferably be leas than 1% and may for example be of the order ot .01 to 1%.

Without the use of promoters the temperature of the reaction is usually within the approximate range of about 350 to 700 F., isoparaiilns such as isooctane requiring temperatures only within the range of 350 to 450 F.' With suitable promoters the temperature may be within the approximate range of 400 down to 200 or even as low as 100 F.

'I'he pressure should be sumcient to maintain substantially liquid phase conversion conditions and will, of course, be dependent upon the temperature employed. Generally speaking, relative- 1y high pressures are necessary, i. e. within the range of about 200 to 2000 pounds per square inch or higher. With benzene, isooctane and hydrogen uoride Aat about 400 F. the pressure may be of the order of about 1200 to 1300 pounds per square inch. With heptane, benzene, and hydrogen iiuoride containing about 5% boron fluoride the pressure may be of the order of about 1000y pounds per square inch for conversion-at about 300 to 330 F.

The contact time or space velocity is likewise dependent to a considerable extent on other conversion conditions and may range from a matter of minutes to a matter of hours. In a batch reactor good conversions have been obtained with contact times of 4 to 5 hours but in a continuous reactor provided wit-h high speed mixers the contact time may be more nearly of the order employed in conventional isoparailln-oleiln reactions. On a space velocity basis in a continuous system I may employ about .2 to 2 volumes of hydrocarbon charging stock per hour per volume of catalyst in the reactor.

In a continuous system most of the catalyst may be recycled from a settler back tothe reactor and the hydrogen fluoride recovered from the product and from spent catalyst or complex ma-l terial may be employed as a scrubbing liquid for preventing losses of boron uoride promoter with hydrocarbon gases which are vented from the system. By recycling selected fractions of the product I may direct the reaction toward the -iormation of particular alkyl benzenes, aviation blending stocks, etc. The invention will be more clearly understood from the following detailed description read in conjunction with the accompanying drawing which forms a part of this specification and which is a schematic ilow diagram of my improved alkylation system.

An aromatic hydrocarbon such as benzene. an

alkyl benzene or a benzene-alkyl benzene-mixture is introduced from source I by pump I I to charge operates at atemperature of about 400 F. and at a pressure o! about 1300 pounds per square inch. 'I'he heat exchanger I5 may be/in line I2-prior to the juncture of line I5 therewith or instead of employing a heat exchanger I may employ a' jacketed reactor or any other conventional means of temperature control. The reactorin this case may be. provided with a high speed stirrer I8 although it'should be understood that instead oi a. stirrer I may obtain the intimate mixture by the use of circulating pumps either within the reactor itself or outside oi' the reactor in accordance with conventlonal'practice in, isoparasin-alcun alkymuen systems. Themixture of' catalyst and hydrocarbons passes from reactor I'I by line I9 to settler 20 whichA may be operated at substantially reactor temperature and pressure. It should be understood. however, that a cooler may be employed in line I3 in order to facilitate the settling ,of the hydrogen uoride catalyst from the hydrocarbon layer in the settler and that the settler may operate at any temperature within the approximate range of 100to 400 F. The settled catalyst may be withdrawn through line 2I and returned by pump 22 and line I5 to the reactor.

The hydrocarbon stream may be passed through line 23 and pressure reducing valve 24 to hydrogen iluoride stripper 25 which in this case is an azeotropic distillation still provided with a suitable heater or reboiler means 26 at its base.' An hydrogen uoride-butane azeotrope passes overhead through line 21 to cooler-condenser 28 and settler 29. 'I'he condensed mixture separates into line I2. A paraffin hydrocarbon, preferably an Isoparathn or a mixture of isoparaillns such as isobutane, methyl pentanes, isooctane, etc. or a mixture thereof, is introduced from source I3 by pump I4 to charge line I2. Hydrogen iiuoride is introduced to charge line I2 from line I5 and the mixture of catalyst and hydrocarbon charging stock may be introduced through heat exchanger I6 to reactor I1 which inA this case a lower hydrogen uoride layer which is withdrawn through line 30 and introduced by pump 3| either through line 32 to line I5 or through lines 33 and 34 to absorber 35. The upper butane layer passes over the weir in the settler and is returned by pump 36 in line 31 to stripper column 25.

'I'he product stream which leaves the base of stripper 25 through line 38 may be passed through a bauxite or other conventional treating system for the decomposition and/or removal of'alkyl fluorides but since no olens are employed in my system the use of such a treating system is usually not necessary. The stream from line 38 passes from debutanizer tower 39 which is provided with a suitable heater or reboiler 40 at its base. The overhead from tower 39 is condensed in cooler 4I and introduced into receiver 42 from which any uncondensed gas may be vented through line 43. A part of the condensate withdrawn from the receiver by pump 44 may be returned by line 45 for reflux in tower 39. The remainder of the condensate may be withdrawn from the system through line 46 or returned by line 41 to reactor charge line I2.

The bottoms from tower 39 are introduced through line 48 to isopentane-neohexane tower pentaneneohexane blending stock for aviation gasoline. l

The bottoms from tower 49 are introduced through line 56 to recycle tower 51 which is provided with a suitable heater or reboiler 58 at its base. The overhead from this tower may consist of hydrocarbons boiling within the approximate range of 140 to 260 F., i. e. it may contain benzene, toluene, methyl pentanes, methyl hexanes, etc. The overhead stream is condensed in this line will likewise leadto the base of absorber 35. When boron fluoride is employed it may be cooler 59 and introduced into receiver 60 from uct stream. When the conversion conditions are such as to produce" substantial amounts of ethyl benzene tower 65 may be so operated as to take overhead a stream consisting chiefly of this hydrocarbon. Alternatively, the overhead from tower 65 may be employed as a blending stock for high knock rating motor or aviation fuel.

The bottoms from tower 65, which is provided with suitable heater or reboiler 1 I, are introduced through line 12 to highboiling products tower 13, which is provided with heater or reboiler 14. The overhead from this tower is condensed in l,cooler 15 andintroduced into receiver 16, a part of the condensate being returned' by pump 11 and line 'I8 for reflux and the remainder being withdrawn through line 19. If desired a higher boiling heavier product such as tertiary butyl benzene may be withdrawn as a side stream through line 80 or recovered in a separate i'ractionating tower. Higher boiling componentsare withdrawn through line 8|.

A portion ofthe settled catalyst may be withdrawn from line 2| through a pressure reducing valve in line 82 to hydrogen fluoride recovery drum 83 which is provided with suitable heating' means 84. This drum may operate at substantially atmospheric pressure and at a temperature of about 100 to 150 F. Thehydrogen fluoride is taken overhead through cooler-condenser 85 to receiver 86 and the condensate may be passed by pump 81 either through line 88, through line I5 or through lines 89, 33 and 30 to absorber 35. Spent tarry material may be withdrawn from the base of drum 83 through line 90. By the simple means hereinabove described catalyst losses may be reduced to such an extent that they are practically negligible.

When a promoter such as boron fluoride is employed it may be introduced from source'SI by pump 92 to chargeinlet line I2. Most o'f the boron fluoride will remain in the catalyst if high pressures are maintained in settler 20. However when boron fluoride is employed it may be desirable tooperate settler 20. at a lower pressure so that boron fluoride may be withdrawn from the top of the settler through line 93 and` conveyed to the base of absorber 35 wherein it is countercurrently scrubbed at a pressure of the order of 500 to 1000 punds or more per square inch with hydrogen fluoride introduced through line 34, any

. required make-up hydrogen fluoride being introduced from source 94 by pump 95. At such pressures and at substantially condenser-water temperatures the boron fluoride is selectively absorbed in the hydrogen fluoride and any' hydrocarbons may be vented from the .system through line 96. The hydrogen fluoride from the base of the tower is passed by line 91 and pump 98 to line I2. Any gases which accumulate in settler 29 may be vented through line 99, and it desired desirable to introduce the bottoms from drum 83 'to a settler for recovering aromatic hydrocarbons and to heat the residual spent catalyst complex material toa temperature of 300 to 350 F. for decomposing the complex and recovering hydrogen fluoride and boron fluoride.. The recovered hydrogen 'fluoride and boron fluoride may be either introduced at the base of absorber or charged to the reactor through line I2.

Results obtainable by the use of my invention are shown by a batch run wherein 4.2 mois of benzene were stirred with 2.1 mols of isooctane (2,2,4- trimethyl pentane) in the presence of 4.5 mois of anhydrous hydrogen fluoride in a stirred bomb reactor at a temperature of approximate'- ly 400 F. under a pressure of approximately y1300 pounds per square inch for a contact Fractionation time of approximately 5 hours. of the product in this case showed a yield of 65% of theoretical for tertiary butyl benzene based 'on the octane charge. 'Ihe product consisted almost entirely of gas (isobutane), unchanged benzene and isooctane, thev tertiary butyl benzene,

and a very small amount of high boiling material whichdid not solidify at room temperature. The

absence of dibutyl benzene in the product was unexpected and renders the process advantageous fortertiary butyl benzene production.

With regard to the use of an activator with hydrogen fluoride a run was made wherein 298 parts by weight of heptane, 232 parts by weight of benzene, 373 parts by weight of hydrogen fluo'- ride and 19 parts by'weight of boron fluoride were introduced into a bomb and intimately contacted by rapid stirring at a temperature oi' about 330 F. to a pressure which rose from about 700 to 1070 pounds per square inch during the reaction time of about 50 minutes. Practically no hydrocarbon gases lighter than propane were produced and the complex formed only amounted to about 20 parts by weight. In a similar run employing aluminum chloride and hydrogen chloride the complex formation amounted to about 196 parts by `weight---practically ten times the amount of complex produced in the hydrogen fluorideboron fluoride run. The extremely small amount of complex produced and the. facility with which catalyst can be recovered from the complex are important features of the invention.

In this second run with boron fluoride promoted hydrogen fluoride -32 weight percent of condensibles were produced of which approximately 33% was propane and 67% isobutane with no determinable amount of normal butane in the products. 'Ihe process thus provides a method for producing isobutane of remarkable purity.

The C5 and heavier hydrocarbons amounted to about 68 weight percent of the total hydrocarbons charged and the analysis of the C5 and heavier hydrocarbons on a volume percent basis was as follows:

Since the recycled hydrocarbons in the system illustrated in the drawing consist essentially 'of aromatics and isoparamns the normal charging stock may be converted almost quantitatively into particular alkyl benzenes, high knock rat-1 ing aviation blending stocks, isobutane and heavier hydrocarbons. Alkyl benzenes such as ethyl benzene, isopropyl benzene and butyl benzenes' are valuable for the preparation of styrene and styrene derivatives and for many other organic syntheses.

While I have described in` considerable detail a spccic system for practicing the invention on a continuous basis it should be understood that 'iiuoride at a conversion temperature under a pressure suilicient to maintain substantially liquid phase conversion conditions and with suillcient time oi contact to effect the production of an alkyl aromatic hydrocarbon and an isoparailinic hydrocarbon, and separating an alkyl aromatic hydrocarbon and an isoparailinic hydrolcarbon thus produced.

2. The process of claim 1 wherein the parafilnic. hydrocarbon charging stock is an isoparaiiln.

3. An alkylation process which' comprises contacting an aromatic hydrocarbon and a parafnic hydrocarbon with a catalyst consisting essentially of hydrogen fluoride and between about 2 per cent .and about 20 weight per cent of boron iluoride at an alkylation temperature not substantially higher than about 400 F. under a pressure suicient to maintain the liquid phase for a. period of time suiiicient to produce an alkyl aromatic hydrocarbon and an isoparailinic hydrocarbon, and separating an alkyl aromatic hydrocarbon and isoparaiiinic hydrocarbon thus produced.

4. The process of claim 3 wherein the parainic hydrocarbon charging stock is an isoparaiin.

5. The process of claim 3 wherein the alkylation temperature is between about 200 F. and about 400 F.

6. A hydrocarbon conversion process whichcomprises contacting a mixture of an aromatic hydrocarbon and a paralinic hydrocarbon with a catalyst consisting essentially of hydrogen fluoride promoted by about 2 to about 20 weight per cent of boron fluoride in a liquid phase conversion zone maintained at a conversion temperature, withdrawing products from said conversion zone to a settling zone, returning a liquid catalyst layer from said settling zone to said conversion zone, separating a gas stream comprising boron nuoride from said products withdrawn from said conversion zone and returning the boron iluoride of said gas stream to said conversion zone. introducing hydrocarbon products from said settling zone into a hydrogen fluoride recovery zone, separating hydrogen fluoride from said hydrocarbon products by azeotropic distillation with a normally gaseous hydrocarbon product in said lastnamed zone, returning recovered hydrogen iiuoride to said conversion zone, and subjecting the hydrocarbon products from which both boron iluoride and hydrogen uoride'have 'been removed to a fractionating step.

wv 7. The process of claim'6 which includes the further steps of introducing liquid hydrogen nuo. ride at a lowv temperature into-the top of an absorbing zone, introducing said gas stream comprising boron iiuoride separated from 'said products into the base of said absorbing zone. drawing unabsorbed hydrocarbons from the top of said absorbing zone, and introducing hydrogen iiuoride with absorbed boron fluoride from the base of said absorbing zone into said conversion zone.

8. The process of claim 6 wherein the parafiinic hydrocarbon charging stock is an isoparafiin.

SAM B. BECKER.

so 'REFERENCES CITED The following references are of record in the iiie of this patent:

UNITED STATES PATJLN'IS Number` Name Date 2,088,598 Ipatieff et al. (I) Aug. 3, 1937 2,098,045 Ipatiei et al. (II) NOV. 2, 1937 2,169,494 Ipatieff et al. (III) Allg. 15, 1939 2,234,984 Sachanen et al Mar. 18, 1941 40 2,275,312 Tinker et ai Mar. 3, 1942 2,283,142 Ipatiel et al. (IV) May 12, 1942 2,320,629 Matuszak Jan. 1, 1943 2,333,866 Komarewsky Nov. 9, 1943 2,347,317 Gibson Apr. 25, 1944 1,933,434. Hofmann et al Oct. 31, 1933 2,167,358 Gleason July 25, 1939 2,196,363 Robertson Apr. 9, 1940 2,340,557 Pines et al Feb. 1, 1944 2,343,744 Burk Mar. 7, 1944 5U 2,345,095 Bruner et al Mar. 28, 1944 2,354,565 Wood et a1 July 25, 1944 2,373,303 Frey Apr. 10, 1945 2,385,300 -Pines et al. (II) Sept. 18, 1945 2,403,649 Frey July 9, 1946 OTHER REFERENCES Simons, Potential Uses Chemical Processes. Ind. and Eng. Chem., vol. 32, page'l81 (l page), Feb. 1940. (Patent Oiiice Library.) 

